Moisture teller



June 11, 1963 H. w. DIETERT MOISTURE TELLER 2 Sheets-Sheet 1.

Filed. June 20. 1961 Poum SUPPLY NI ,r m a Y M M 0 v. 11 B June 11, 1963 H. w. DIETERT MOISTURE TELLER 2 Sheets-Sheet 2 Filed. June 20. 1961 arrorfizra.

United States Patent 3,093,460 MOHSTURE TELLER Henry W. Dietert, Kerrville, Tex assignor to Harry W. Dietert Co., Detroit, Micln, a corporation of Michigan Filed June 20, 1961, Ser. No. 118,399 1 Claim. (Cl. 34--1) The invention relates to moisture tellers and refers more specifically to a method of and apparatus for drying granular material including electronic means for vaporizing the moisture in the granular material.

This application is a continuation in part of United States patent applications Serial No. 273,270, filed February 25, 1952, and Serial No. 60,147, filed October 3, 1960.

In the past drying apparatus for removing moisture from granular material, such as foundry sand, in determining the percentage of moisture therein have been relatively slow in evaporating the moisture. Further, with prior drying apparatus the heat necessary to evaporate the moisture has unnecessarily elevated the temperature of the drying apparatus. Additionally in the past it has often happened that moisture evaporated from the specimen being dried has condensed on the surfaces of the drying apparatus impeding the drying ability thereof.

Attempts have previously been made to provide drying apparatus which alleviate these problems. For example, it has in the past been the practice to blow heated air through the drying apparatus to remove the evaporated moisture therefrom to prevent condensation thereof on the drying apparatus. Also, infrared radiators have been used as heating elements to more rapidly heat the specimens to cut down the time required to make a moisture determination.

Such prior art drying apparatus have however not been entirely satisfactory in that the time required to remove the moisture from a specimen cannot be sufiiciently reduced thereby and the temperatures created thereby over the necessary periods of use are objectionable in that they present a danger to operators and unnecessarily elevate the temperature adjacent the drying apparatus. Further blowing of air through the drying apparatus at a temperature below the boiling point of the evaporated moisture has been ineffective to prevent objectionable condensation of the moisture on the drying apparatus.

It is therefore one of the objects of the present invention to provide means for more rapid drying of a specimen of granular material than has previously been possible.

Another object is to provide drying apparatus including high frequency electronic means for evaporating moisture.

Another object is to provide a method of drying granular material including electronically evaporating moisture from the material to be dried.

Another object is to provide a method of drying granular material including heating air to a temperature above the boiling temperature of the moisture to be evaporated from the granular material and blowing the air through the apparatus in which the granular material is being dried.

Another object is to provide drying apparatus including means for developing a high frequency electric field, means for supporting a sample of foundry sand within the electric field and means for blowing air heated to a temperature above the boiling temperature of the moisture to be removed from the foundry sand through the drying apparatus.

Another object is to provide drying apparatus com- 3,093,460 Patented June 11, 1963 prising a closed cabinet, a conducting grill supported by insulating means within the cabinet for receiving a sample of granular material supported by filter paper, glass or the like, a grounded electrode positioned on the opposite side of granular material from the conducting grill within the cabinet, means for generating a high frequency electric field between the grill and grounded electrode, means for heating air to a temperature above the boiling point of moisture within the granular material and blowing the air through the grill and cabinet.

Another object is to provide drying apparatus as set forth above including a wave guide for directing a high frequency electric field between a micro-wave generator and a grounded electrode through the granular material.

Another object is to provide drying apparatus including a pair of electrodes, means for creating a high frequency electric field between the electrodes, means for blowing heated air over the electrodes, a balance, means supporting a sample quantity of granular material from which moisture is to be removed within the high frequency electric field from one end of the balance.

Another object is to provide a method of and apparatus for drying granular material which is simple, economical and efficient.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, illustrating a preferred embodiment of the invention, where- FIGURE 1 is a diagrammatic representation of drying apparatus constructed in accordance with the invention.

FIGURE 2 is a modification of the drying apparatus illustrated in FIGURE 1.

FIGURE 3 is another modification of the drying apparatus illustrated in FIGURE 1 wherein the means supporting the sample of granular material within the high frequency electric field is a balance for providing a direct indication of the moisture content of a sample of granular material.

With particular reference to the figures of the drawings, one embodiment of the present invention will now be disclosed.

As shown in FIGURE 1 the drying apparatus 10 of the invention comprises a cabinet 12 including a support 14 therein for a sample 16 of granular material such as foundry sand which is to be dried. The high frequency oscillator 18 and means 20 for transmitting the high frequency signal generated thereby through the sample 16 of granular material is also a part of the drying apparatus 10. Heating means 21 including blower 22 and heater 24 is provided to blow air through the cabinet 12 which is heated to a temperature above the boiling point of the moisture to be removed from the granular material 16.

More specifically the cabinet 12 includes the base 26 and the vertical walls 28 secured to the base 26 by convenient means (not shown). A cover 30 is hinged to the vertical walls 28 by hinge 32, as illustrated in FIGURE 1 to permit entry into cabinet 12.

Support 14 includes a hollow support 34 constructed of insulating material such as a ceramic positioned Within the cabinet 12 and holds the grill 36 at one end thereof. Grill 36 is of conducting material such as, for example, perforated aluminum. The grill 36 serves as a support for a sample carrier 38 which is preferably of filter paper or may be glass, plastic or the like.

The base 26 of the cabinet 12 is provided with an opening 40 therethrough in which the insulating support 42 for the transmission means 20 is secured.

Wall 28 of the cabinet 12 and the support 34 are provided with aligned openings 44 and 46 respectively therein through which the conduit 48 extends. Conduit 48 is part of the heating means 21 which, as previously indicated, also includes the blower 22 and heater 24. In operation the blower 22 which may be energized from an electric source (not shown) through conductors 50 is effective to blow air over the heater 24 which also may be energized from a source of electric energy (not shown) through conductors 52.

The heater 24 is then effective to heat the air to a temperature slightly above the boiling point of the moisture contained in the sample 16 of granular material positioned over the grill 36. The air thus passed through cabinet 12 which may be exhausted therefrom by normal leakage from the cabinet 12 or through an exhaust port 54 is caused to evacuate the evaporated moisture from the cabinet 12 and thereby prevent condensation of the moisture therein.

The electronic means for producing the electric field in which the sample 16 of granular material is positioned includes the micro-wave generator 18 which may be of any known type operable to produce an electric signal having a frequency of between 1700 kilocycles and 2500 megacycles. One particular frequency which has been successful is, for example, megacycles.

The means 20 for transferring an electric signal from the oscillator 18 to the conducting grill 36 is held in position by means of insulating material 42. The grounded electrode 56 on the opposite side of the sample 16 of granular material to be dried from grill 36 forms the other electrode between which the high frequency electric signal which functions to evaporate moisture from the specimen of granular material 16 positioned therebetween is produced.

Thus in over-all operation a sample of granular material having moisture therein which it is desired to remove therefrom is positioned on a container 38, such as filter paper, and is placed in the cabinet 12 on the grill 36. Blower 22 and heater 24 are then turned on so that air heated to a temperature slightly above the boiling point of the moisture in the granular material is passed through conduit 48 into support 34 through grill 36 around the sample of granular material 16 thereon into cabinet 12. The micro-wave generator or oscillator 18 is then energized to produce a high frequency electric field between grill 36 and electrode 56 whereby due to dielectric heating the moisture in the granular material is vaporized.

The vaporized moisture is not however allowed to condense on the drying apparatus 10 since the heated air is at a temperature above the boiling point of the moisture and therefore carries the moisture still in a vaporized state out of the cabinet 1'2. Further since the high frequency electric field does not function to cause dielectric heating in conductor materials to any appreciable extent the cabinet, grill and electrode may be maintained at a relatively low temperature.

Extremely rapid drying of granular material is thus accomplished. For example, it is possible with a 15 megacycle electric signal to dry a fifty gram sample of granular material in approximately thirty seconds.

The modification 58 of the drying apparatus 10 illustrated in FIGURE 2 includes the cabinet 60 having a sample compartment '62 and a heated air duct 64 separated by a perforated grill 66 of conductive material. A sample of granular material 68 in a container 70 of filter paper, glass or similar material may be positioned in the sample compartment 62 through the door 72. Heating means 74 including blower 76, heater 78 and conduit 64 are provided as before to blow hot air through grill 66 to carry away the moisture vaporized from the granular material sample.

In the modified drying apparatus 53 the high frequency electric field is produced by a micro-wave generator 32 which is energized from a power supply 84 and cooled by means of a cooling blower 86 also energized from power supply 84. The high frequency electric signal is then directed toward the grounded grill 66 in cabinet 60 through a wave guide 83 including baffies 90 extending transversely thereof for directing the electric wave therethrough. Operation of the modified drying apparatus 58 is the same as the operation of the drying apparatus 10.

The modification 92 of the drying apparatus 10 illustrated in FIGURE 3 provides an automatic indication of the moisture content of a sample of granular material 94 as it is dried. The drying apparatus 92 includes the means 96 for producing a high frequency electric field in which the sample 94- of granular material is positioned. Means 98 and 100 are also provided in the modified drying apparatus 92 to blow hot air over the electrodes 102 and 104 of the means 96 for producing the high frequency electric field. The drying apparatus 92 also includes the balance 105 operable to provide an indication of the moisture content of the granular material sample 94 as it is being dried.

The means 96 for producing the high frequency electric field includes a micro-wave generator 106 energized through electrical conductors 168 from a source of electrical energy (not shown), leans 110 for transmitting a high frequency electric signal from the micro-wave generator 106 to the electrode 104, and grounded electrode 102 and electrode 104 between which the sample 94 of granular material to be dried is positioned. In operation the micro-wave generator is energized to produce an electric signal which is transferred to the electrode 104 to create a high frequency electric field between the electrodes 104 and 10?- causing vaporization of the moisture in the granular material positioned between the electrodes without heating appreciably any conducting material of the drying apparatus.

Each of the heating means 98 and 100 comprises a blower 112, a heater 114 energized through electrical conductors 116 from a source of electrical energy (not shown), and a conduit 118. Thus in operation with the heaters 114 and the blowers 112 energized air heated to a temperature above the boiling point of the moisture in the granular material in the sample 94 is directed against both of the electrodes 104 and 102 .to prevent condensation of moisture from the sample of granular material 94 thereon and to remove the moisture from the drying apparatus.

Balance 105 comprises a balance beam 120 pivotally mounted at 122 and having the pivot support 124 at end 126 thereof for the hook member 128. Hook member 128 is secured to a balance tray 1330 for supporting the sample 94 of granular material to be dried. An elongated support member 132 is secured to the other end of the balance beam 120 along which a second hook member 134 having a pivot point 136 thereon may be variably positioned. Hook member 134 supports a second balance tray 138 thereon for receiving a balancing weight.

Thus in operation a sample of granular material is placed on the tray and is balanced by a weight on tray 138. The hook member 134 is positioned to balance the beam 120 about the pivot 122. During drying of the sample of granular material 94 in the manner indicated the weight of the sample 94 on the balance tray 130 will decrease to cause pivoting of the balance beam 120. The pivoting of the balance beam 120 will be related to the amount of moisture in the sample of granular material 94 whereby an indication of the moisture content thereof will be provided.

The drawings and the foregoing specification constitute a description of the improved moisture teller in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claim.

What I claim as my invention is:

Drying apparatus for removing moisture from a specimen of granular material such as foundry sand, comprising an outer container including a bottom having an opening therein olfset with respect to the center of the container which bottom is secured to and closes one end of the outer container, at top at the other end of the outer container for closing said other end, an air intake and an air exhaust opening extending transversely through opposite sides of said outer container adjacent the bottom of the .outer container with the air intake opening substantially closer to the opening in the bottom of the container than the air exhaust opening, an inner container of insulating material having an open lower end positioned within the first container and resting on the bottom thereof, said inner container extending parallel to said outer container and having its center offset with respect to the center of said outer container and positioned substantially over the opening in the bottom of the first container, a perforated conducting member secured over the other end of the inner container for supporting a sample of granular material, a grounded electrode supported in the outer container in a location over the perforated member, a second electrode insulated from and extending through the opening in the bottom of said outer container to the perforated member for directing a field of high frequency electric energy between the perforated member and grounded electrode, means including an oscillator connected to the second electrode for producing and passing through said second electrode a high frequency electric signal, a blower including a conduit extending through the air intake opening in the outer container and emptying into the inner container for passing air through the air intake opening in the References Cited in the file of this patent UNITED STATES PATENTS 2,428,615 Brown Oct. 7, 1947 2,588,811 Dippel Mar. 11, 1952 2,650,289 Hagopian Aug. 25, 1953 2,676,416 Calosi Apr. 27, 1954 2,698,488 Cannon Jan. 4, 1955 2,790,957 Millett Apr. 30, 1957 2,866,063 Rudd Dec. 23, 1958 2,532,460 Phillips Dec. 5, 1960 OTHER REFERENCES Virginia Polytechnic Institute Bulletin, Eng. Experiment Station Series No. 42, Drying Ceramic Products, by use of Induced High Frequency Electrical Energy, by T. C. Vaughan, H. E. Revereomb, W. -A. Murray and J. W. Whitmore, 1939, pp. 120.

Industrial and Engineering Chemistry, vol. 41, 1949, No. 8, pp. 16864694. 

